This invention relates to a top closure for a rectangular box. Various attempts have been made to provide a top closure for an elongated box having an open upper end. Tarpaulins or other flexible sheet members can be rolled across the open upper end of the box to provide a cover. Such a cover has application for covering the tops of truck trailers, for covering the upper ends of bins, or for covering such things as solar collectors.
One problem encountered with flexible covers used outdoors is the exposure of the flexible cover to wind. Means must be provided for holding the flexible cover against movement or billowing in the wind. Furthermore, it is desirable to provide a flexible cover which can be quickly and easily moved from its open to its closed position with a minimum of effort and time.
Means have been provided for rolling a tarpaulin on an elongated shaft so that by rolling the shaft it is possible to roll and unroll and tarpaulin from an open to a closed covering relationship over the open upper end of the box. However, with such devices, it is difficult to keep proper tension on the tarpaulin during rolling and unrolling. Furthermore, during the unrolling operation, it is necessary to face the truck trailer in such a manner that the wind will not catch the tarpaulin. Otherwise, the wind will go beneath the tarpaulin, catch it and perhaps rip or tear it.
Therefore, a primary object of the present invention is the provision of an improved top closure for a rectangular box.
A further object of the present invention is the provision of an improved top closure which is held positively so as to minimize damage to the cover during exposure to the wind.
A further object of the present invention is the provision of a top closure which maintains a constant tension on the flexible cover so as to hold it in tight covering relationship over the open end of the box.
A further object of the present invention is the provision of a top closure having fastening means for fastening the closure in closed relationship over the open upper end of the box.
A further object of the present invention is the provision of fastening means which automatically attach the tarpaulin to the box in response to unrolling of the tarpaulin to its closed position.
A further object of the present invention is the provision of a top closure wherein a substantially constant tension is applied to the flexible sheet member throughout its movement from its closed to its open position.
A further object of the present invention is the provision of a top closure having a power device for automatically unrolling the flexible sheet member.
A further object of the present invention is the provision of a device which is economical to manufacture, durable in use and efficient in operation.
The present invention utilizes a flexible sheet member which is anchored adjacent one edge of the box opening. The sheet member is wound around an elongated shaft and the shaft is guided at its opposite ends by tracks which span the width of the box opening. The shaft is adapted to roll from a first position adjacent the anchored end of the sheet member to a second position adjacent the opposite edge of the box opening, so as to spread the sheet member in covering relationship over the opening. As the shaft moves from its first to its second position, it unrolls the sheet member and causes the sheet member to cover the opening.
A plurality of flexible flaps are connected along the upper edge of the box opposite from the edge to which the sheet member is anchored. These flexible flaps protrude upwardly above the upper edge of the box sidewall.
As the shaft unrolls the tarpaulin towards its closed position, the shaft and tarpaulin engage these flexible flaps and cause the flaps to wrap around and become attached to the shaft. Because the flaps are also attached to the side wall of the box, they cause the shaft and the tarpaulin to be attached to the box when they become wrapped around the shaft. Thus, as the shaft rotates and moves towards its closed position, it engages the flaps and becomes attached to the sidewall of the box.
In order to maintain tension on the sheet member, a spring is attached to the shaft and maintains a constant tension on the sheet member throughout the rolling movement of the shaft from its open to its closed position. The spring is attached to a connecting member extending from the spring to the shaft and the connecting member is attached to the shaft so that the spring will maintain a constant tension on the tarpaulin throughout movement from its open to its closed position.
The shaft may be rotated either by an electric motor or by a hand crank. The electric motor used for the present invention has a track follower which engages the track at a point spaced from the shaft around which the sheet member is wound. Actuation of the motor causes rotation of the shaft so as to cause it to move from its open to its closed position. Because the track follower is spaced from the rotational axis of the shaft, the track follower provides a stabilizing function to the motor to prevent rotation of the motor. The spring also provides further aid in causing the shaft to move to its closed position.
In order to open the closure, the motor is actuated so as to rotate in the opposite direction (or in the case of a hand crank, the crank is rotated in the opposite direction), thereby causing the shaft to unwind the flaps and thereby detach the shaft from the sidewall of the box. Continued rotation of the shaft causes the shaft to wind the tarpaulin upon the shaft and to pull the shaft towards its open position. The winding up of the sheet member causes the shaft to be pulled from its closed position to its open position against the bias of the spring.
The flaps for securing the shaft in its closed position may comprise a single elongated flap which runs along the entire upper edge of the box opening or it may be a plurality of smaller flaps spaced apart from one another and extending along the upper edge of the box adjacent the box opening. These flaps secure the shaft to the sidewalls of the box in such a manner that the wind cannot get underneath the tarpaulin and cause ripping or tearing of the tarpaulin.